He kinda said he didn't know in the video. He said he isn't part of it but there are people working on algorithms to try and use these superpositions as waves.
5km view just to see how it looks like. With the factorization as example (Shor algorithm)... You enter the 2 numbers as wave "periods", once collapsed it will give you the "period" of when the two combined numbers are the same, which is the factor. Imagine 2 gears with different numbers of teeth, the common factor will be the turns you have to do so both gears are at the same position as the start. A classical computer hast to count the turns until it repeats. A quantum computer does it "instantly". Of course "enter" and "give" involves a lot of math and calculations, but basically all the computation is done by manipulating wave properties in a clever way.
@@ByteMe1980 The basic idea of (some) quantum computing is that you expand the state of the qubits into a particular superposition, apply some algorithm, and then carefully undo the initial expansion with some inversion operation so that you measure something with certainty (or near certainty in many cases). Now, as Phil says at the start, it can be mischaracterised if you're not careful, as there's nothing magic about this (the way you set up the quantum state is very precise), and very often the superposition you set up does not have some trivial one-to-one correspondence with the values of classical bits as is typically descibed, but I wouldn't say it's far off.
I very much take this as a compliment! Thank you so much. Contrary to popular belief, confusion is not necessarily something to be avoided in teaching. See the blog post linked in the video information. Philip (Moriarty, speaking in video)
What I appreciate most about prof Moriarty is that he's so vocal about science not knowing - and how that doesn't matter for the science. Why? We don't know. Period. We may know one day, but then there's likely to be more stuff underneath or within that we don't know - science rarely runs out of questions, but we learn more all the time.
I find it similar to how you can still do useful work with a car even if you don’t know how it works. You can still drive it and carry stuff. If you take the time to learn how it works, you can manipulate it to be more efficient or effective, or to build new cars that are better suited for specific tasks. Even if you don’t know why the wave collapses to one of those states, you can still exploit its properties to do useful work.
That slinky demonstration is the best example I've seen to explain harmonics in the string! Thank you! I was not expecting timbre to be related to quantum computing
It would also be a really simple way of showing how the energy in a photon is proportional to the wavelength. Hopefully some middle school teacher steals it.
@@t_ylr that's an amazing connection to make. Can light waves have a similar "timbre"? Can you somehow add light waves of different frequencies together?
@@ButchMarshall Absolutely. In fact, *all* real light waves have a spread of frequency. It might be very, very, very narrow but the only time we have a pure frequency (i.e. a single value that is defined right down to an arbitrary number of decimal places) is for a wave that lasts an infinite amount of time (or spreads across an infinite amount of space) without being disturbed. But this is a mathematical idealisation.... Philip (Moriarty, speaking in video)
@@thequantumworld6960 so what stops us from making qubits using lasers and measuring device? Why the need for these superconducting super chilled interfaces into the qubit?
@@ButchMarshall It's likely a lot easier to control electrons than photons. They're computing with the bits, you have to find ways to perform operations on them and I'm guessing it's a lot easier to do that with electrons. If anyone has any better ideas I'd like to know if there's a real answer.
"Quantum mechanics is simple: it's just wave interference and harmonics." "So we can measure a quantum wave and all its harmonics?" "No, you can't do that, it'll stop moving and lose all its harmonics." "Why?" "No one knows."
No we do know. Adding energy to the system, by shooting a photon at it or having it hit a detector collapses the harmonics into a single macro state. Like putting your finger on the bass string directly changes its timbre.
@@ac.creations That's not explaining what happens though, that is just an explanation of what can cause a collapse, but not what happens during the collapse.
There are two theories. Copenhagen Interpretation: The waveform instantly collapses into one state upon observation. Many-Worlds Interpretation: The waveform never collapses. Upon observing, the observer becomes "entangled" with the waveform, meaning that both the original waveform and the observer's waveform are in one big superposition. The waveform looks like it collapses to you because you are now part of it.
@@samuelthecamel Why does that lead to "many worlds"? Ok, so I'm entangled with a waveform, why does that make the universe split (I know that's not accurate terminology, maybe "branch" is better)?
This is hands down the best video I ever watched on Quantum Mechanics, and I’ve watched a fair few. I love how Phil isn’t afraid to use analogies, but also tells us where the limits of the analogy are, and his dedication to being accurate even in his layman’s explanations reminds me of Richard Feynman’s approach.
Precisely! It's both simple and intuitive while not shying away from the big picture. Vey Feynman-like Indeed. Takes a lot of skill to come up with explanations like that. I wish I had that kind of talent. I tend to complicate things more when I try though.
"If you can answer that question, you get a Nobel Prize." That's a pretty funny answer to the question "Why?" about a part of quantum physics that does confuse people.
@@ZT1ST Of course it confuses people. It confuses physicists too! The measurement problem is unresolved. Would you prefer that I made up some explanation or pretend that parallel universes are the answer (on the basis of zero empirical evidence)? Philip (Moriarty, speaking in video)
"I don't know... yet" is like job security or printing money to scientists. Really plays into that part of our lizard brains that likes random chance, like what if we find out and it's really valuable. Just to make it sound a little less noble, a little more real.
That's fair enough though. Scientists LIVE for the day they can find out what they don't know, its almost as great as when you actually figure it out :D
@@CaptainWumbo I whish this was true...but the reality is not a lot of money is lining up to fund research where the answer is "I don't know" to the question "How will this be valuable"
I've learned more about Quantum Computing and Quantum Mechanics from a few computer file videos with Professor Phil Moriarty than I have from a lifetime of 'documentaries' and hyperbolic articles. His ability to elucidate and cut through the bull is fantastic. Genuinely appreciate his enthusiastic but humble approach to communicating traditionally mystified topics.
As a former jazz pianist with excellent ear but no background in science, this video makes perfect sense. If you play a low bass note on a piano, you can hear almost as much mid and treble as you can hear bass, and if you listen carefully you can hear all the harmonic notes in the sequence, but everything must all balance out to being most 'probably' (definitely) the note that it is.
I understood that from my experiments in audio DSP. This gives me the courage to think that if I delve deeper into this I may actually understand more. It's the first time I ever imagined that I might grasp what this is all about.
I have always loved this guy's passion and overall demeanor when he talks about his field of science. He gets me pumped up when he gets so excited and passionate about whatever he's talking about.
At 7:36, if Quantum Computers compute via wave interference, why aren't they just considered classical, analog computers? Wave interference is a very classical physics phenomenon being used for computing. You say the word "states", but does that just mean the analog, waveform shape at a particular time?
At 8:57, is a "Quantum" explanation, but it seems that the classical, analog waveform being measure is a resonance *"state"* (or one of the overtones). Again, this still seems very classical. In terms of "Quantumness," is it because we just don't know which resonance *"state"* will be measured?
Sincerely, I think this is the thing missing in this video. - a clearer explanation of how quantum computing computes. For what I understood the quantum computation comes nt from "waveform shape at a particular time" but the multiple combinations of the various single"waveform shapes at a particular time". That is why he reject the notion that quantum is the result of infinite computation. The best I could grasp is that quantum computing aggregates the probabilist result of the many variation of the waves a particle - qubit - can generate from a given input. Again, I mgiht be wrong, but whan Ive saw explained differently, the difference from clasical computing is that the output is either 0-1. In quantum the result comes in terms of probabilites: from all the positions that the wave represeting this qubit uccupied uring the calculation, which is the most probable output. The benefit apparently comes from the fact that you can do with one qubit the calculations one could do with many bits.
@@mustavogaia2655 ** This would be like an analog computer that used overtone/harmonics of a fundamental wave to do computing. ** But, if you get these random energy peaks or random position peaks when you measure the wave, can you build a computer based off of random number generation? i.e. qubits seem to just produce a random number when measured.
@@itsbs Yes, but this would be considered a single quantum operation. Again, not an expert, but the "peaks" are dependent on the function/matrix the is passed thru.
What you neglected to explain is what exactly is special about quantum computing. If we could do those calculations on any wave system - there are much easier ways to do it from pendulum systems to vibrating strings. But we don't see guitar calculators - so there is something special about quantum that allows certain types of parallel algorythms to work incredibly fast.
i definitely understood it better than EVER before! is like polyphonic singing or overtone singing. treating particles as voice, they have many overtones but when meassured (meaning extracting energy from the particles to excite sensor and let it know there is something) the energy drops and falls into a single overtone. which will vibrate over time and make new multiple pletora of overtones again. soo cool!!!
As someone who is confused by many videos on quantum mechanics etc I found this helpful but I wish it had gone further. How can we derive a one or zero from a wave when making the measurement seem arbitrary? I don’t get it, he said over and over.
I think that was skipped because the answer can be quite involved and mathsy. That's the weird part he alludes to, ie. the truly quantum part, rather than just superposition/wave mechanics. There's no reasonable analogy you can make from a quantum superposition collapsing to a guitar string oscillating. A qubit's superposition collapsing into either zero or one is pure quantum mechanics: energy levels turn out to be discrete, not continuous, so in this case it must pick one energy level or the other (which we label as zero or one) when we measure it, not somewhere in between. How that measurement actually physically works in a quantum computer I'm not sure, but there are lots of ways to disturb a quantum superposition and it happens all the time without our involvement. On the maths side of things, most of the time we can't derive a one or a zero from a qubit's superposition with certainty, even if we have perfect knowledge of its state. We can only derive the _probability_ that a qubit will be zero or one when we measure it. What state it actually ends up in is random, based on that probability distribution (or at least, that's how it appears to us). The clever and difficult part of quantum algorithms is manipulating the qubits/superpositions so that they interact in such a way that they calculate something useful while also ensuring when we do a measurement we get the answer we want with certainty _or_ with high enough probability that if we run the algorithm a few times we end up with the right answer. Honestly, I only have a vague high level understanding of this because the nitty-gritty of how it works involves a lot of linear algebra. For a concrete example, minute physics has a great video on Shor's algorithm, and 3blue1brown has some very helpful explanations of the maths involved. (context: I took a couple quantum computing units I didn't have enough time to understand in detail, so I'm far from an expert)
The ones and zeroes are measued with probabilities that are determined by the quantum algorithm. In an ideal scenario, the probability of measuring the correct result is 100%, but it usually isn't quite that simple.
It's a 15 minute video. You're not going to get a detailed, blow by blow analysis of quantum computing/quantum mechanics in 15 mins! I teach the first semester of our Quantum World module, which is 12 weeks of tuition, involving a total of 37 videos, eight worksheets, 12 in-person teaching sessions, and many other tutorial/exam/revision sessions... ...and still we barely scratch the surface of quantum mechanics. One key issue with TH-cam "edutainment" is the idea that complex, complicated questions have straight-forward answers that can be expressed in a clickbait video title. As Feynman said when asked to describe "in a few sentences" the work for which he won the Nobel Prize: "If I could explain it in a few sentences, I wouldn't have won the Nobel Prize." The blog post linked in the video information (and the other posts/articles in turn linked in there) provide a lot more background and information. But the intellectual heavy lifting when it comes to understanding a subject like QM has to come from the learner, not the teacher. Sorry for such a long reply but this is an aspect of TH-cam edutainment that particularly exercises me! Philip (Moriarty, speaking in video)
@@thequantumworld6960 Really interesting to hear that first hand Philip. You and some of the others over at Sixty Symbols did a video years ago about the state of high school physics and the public perception of the subject... it would be interesting to hear more from you about what you think this big world of TH-cam physics/maths/science videos needs to be careful about and how one should go about getting the balance between detail and engagement correct.
At 12:23, when you make a measurement, are you just getting a random energy peak that doesn't match the original wave form? If you measure for position, you are getting another, seemingly random answer. Are Qubits just natural random number generators?
Yes!, but you do know all the possible outcomes or energy peaks you could get, you can then recreate (by repeating the same experiment a lot of times) the (probability) distribution of peaks that makes up your initial wave form. And yes, there are experimental proposals of random number generators using qubits, for example using single photon generators and beam splitters.
@@Miguel_Noether ** So it is like you are random sampling a waveform. It still seems very classical, analog, so how can you make a computer out of this natural, randomized feature?
@@itsbs I don't think I could give you a general answer. You could look for the Grover algorithm which consists in looking for an item stored in a list. The key idea is that you let you quantum computer work on "these distribution of peaks". At the last moment when you do your measurement, the algorithm makes that distribution in such a way that if you do the experiment a lots of times you will almost in all cases get the state representing the item you are looking for.
@@Miguel_Noether As a lay person to quantum computing. Thats what I took from this video as well. First time I felt I had a rudimentary understanding of how the heck one works. It also cemented the idea of why quantum computers are great for highly complex problems. And would be foolish to use for most things classical computers are currently doing for consumers. Why Phil points out how coding for quantum is a whole different subject. If I follow the examples here. Classical logic gates perform a single function per cycle. Whereas quantum qbits can extract multiple (infinite?) data points per "cycle"? Its all dependent on how the coding of the quantum computer was structured. It sounds like coding a quantum computer is more difficult than making the computer itself.
This might be one of my favorite Moriarty videos yet. I feel like I've said this about basically every single one that came out before this, though 😅 As a layperson who's been curious and studying the subject casually for some time, this really feels like a great sweet spot between the whole "quantum is wooonky" and "quantum is just plain math" attitudes you see here and there.
Thank you for explaining that superposition does not mean "every possible position all at the same time." I have heard this description almost exclusively, and it never made sense to me. I chalked up the "doesn't make sense to me" as being inherent in the fact that it is quantum mechanics. While I, of course, don't understand quantum mechanics much better now than before... I do have a better handle on what questions I need to ask.
I'm glad I'm not the only one frustrated with all the "QC explained in 10 minutes" videos. They all can be summarised as "I'll restate the confusing part and pretend that's the explanation for it."
Not mentioned in video, but key to quantum computing is the ability to manipulate the probability of the collapsed wave function using microwave pulses. That's what quantum gates and circuits are for.
Yes, and hopefully we'll get to this in a future video. The entirety of quantum computing/quantum mechanics is not going to be explained in a 15 minute video... Philip (Moriarty, speaking in video)
This is something I still wish to understand. From the start of learning about QC, I wondered what substituted the logic gates of classical computers with a device that can have countless states as output. Seems Im slowly getting there thanks to these and other videos. I also have to think (I could easily be mistaken), we are currently coupling QC with classical ones, to make sense of the massive amount of information they generate? Its easier (for me) to think of QC as standalone data output devices rather than a full blown computer unto itself? In a world were we have grown up around classical computers up till now. Seems nearly impossible to build a purely QC ground up with a user interface? I kinda think of it like a D/A A/D converter. QC into classical??? Then the obvious issue of needed bandwidth to pull this off. Dunno... Still trying to understand it all. Slowly but surely.
The course I took on acoustics gives me a little bit of a leg up on understanding this, as I knew precisely where Dr. Moriarty went with the accumulated sine waves expressing the timbre of the sound and how it applies to quantum computing. Imagine using the Fast Fourier Transform algorithm to assist in quantum computing. Very interesting video... hats off!
Great point! Fourier transforms are absolutely core to quantum mechanics (and therefore quantum computing.) See the blog post linked in the video information (and the links therein) for much, much more on Fourier's role in QM. Philip (Moriarty, speaking in video)
those were all amazing analogies that, except for one, i hadn't heard before, and that may be one of the best overall introductions to the subject i've heard. very fun.
Maybe the physics we call "classical" are just narrowly applicable on specific energy levels, which are the levels we exist at -- whereas most of the universe is either near absolute zero, or at extremely high energy levels. And when we "measure" something, we're just reducing the temporal dimension (an "instant" to us) to where it behaves like the everyday physics we are familiar with. Sort of like how an ocean would appear like a solid if you interacted with it at 0.01 frames per second -- but behaves like a wavy liquid at 100 frames per second.... if that makes sense
yeah that's very similar to my own pet theory of what's going on. If we consider time as we understand it to be the 4th dimension of our existence with things like how gravity can bend "spacetime" and whatnot, electrons at a quantum level could be thought of as existing at a dimensionality beyond our 4 intuitive dimensions. If we also add to this the concept that time exists at the finest level with a discrete smallest unit of time (there exists a unit of time that cannot be divided), the issue of "probability" in measurement could be that when we attempt to measure the electron in our limited 4 dimensions we are actually "collapsing" 5 or more dimensions into just 4 to get our measurement, thus why the wave collapses into a single state since our action of measuring in 4 dimensions causes us to "hold constant" any other dimensions at play, thus destroying the harmonic (take a 2 dimensional wave-form, and force it into 1 dimension to take a measurement, you can't return now to the original 2 dimensional state) -- Wish I knew enough to work out this theory a little further, it's very interesting to think about.
I like that. Problems like this (I believe) probably depends heavily on relatively and our 3 dimensional observations. The energy levels we're used to interacting with also coexist with the only life (that we know of) in our small sliver of the universe..... so how do we know gravity doesn't bias our answers? The universe as we know it is mostly empty space, and we happen to be conducting all of our experiments really close to a fairly large mass, which as we know has an effect on our perception of time... Think about this, if a small object (baseball) is released next to another object with significantly greater mass (planet), the ball will appear to be getting closer to the planet (relative to the planet) and the planet will appear to be getting closer to the ball (relative to the ball), yet an outside observer will clearly see the ball moving towards the planet (the right answer?) The fact that there's 3 different conclusive answers to this one measurement isn't weird, it's relativity, but what happens if you can't become the third observer? How do we even know when we are the third observer when measuring something? Can you prove when we are?
The only ones who've ever attempted to describe how D-wave works are D-wave themselves, last time I checked. I've never been convinced by their explanations that what they're doing actually "works" and I've never seen an application for what their systems might be able to do for a business, certainly not versus a cost analysis.
Does Professor Moriarty have his own TH-cam channel? I'd be interested in seeing some longer form content from him. I always enjoy the videos with him in them.
Hi, @PBJ AND A HIGHFIVE. Thanks so much for asking. Yes, I have a channel, "The Quantum World", which features videos for our 2nd year undergraduate physics course of the same name. Click on the avatar... Philip (Moriarty, speaking in video)
...but it's all the same! Wave mechanics and matrix mechanics are the same principles, just expressed in a different "language". A function can be thought of as a vector in a high dimensional space... Philip (Moriarty, speaking in video)
I think I finally ... well, not get it, but, I'm pretty sure this is the closest to understanding how I should be thinking about the concept so far. Excellent video. Again professor Moriarty is inspiring me to use my uneducated software developer brain to really get my head around computer science, maths and physics. Thank you
At 9:32, when porting the guitar string analogy, why wouldn't you use Schrodinger's Wave Mechanics? In other words, apply Schrodinger's explanation of "charge density" of the electron medium energy that you are detecting, instead of thinking about it as the probability of detecting an individual ball/sphere electron particle?
@@Miguel_Noether ** I see them opposites... like water in a lake (medium) versus a billiard ball (particle). When particles collide, they bounce and scatter. When waves in a medium collide, the pass right through each other. Opposites...
At 9:15, I thought the answer was going to be something like: -Just like the string of the bass, if you take a picture of the string vibrating (you measure it), your measurement is going to be standing still in time (pictures don't move) and as such, the string is going to look like it is in one of those states (more to one than the others), but if you measure it again, it may look more like another state now (as the string continued to vibrate before you took another picture). So... the reason the measurements are in a random superposition, is because the wave is vibrating, through time. But when you measure it, your measurement is standing still in time, and is a mere snapshot of where it was at a random point in time. Waves exist through time; measurements stand still. You could make a metaphor of trying to take a frame out of a movie. It's all blurry because there is no time element. No wave; just a measurement. The wave collapses into one of the states because measuring means taking the element of "time" out of the system. Does that make sense or am I missing something? Pardon my bad English. Feel free to correct me anytime.
Also, let's say you have infinite modes of vibration (as in 5:20). Your measurement would be like a list of probabilities, right? -mode 1: 8% -mode 2: 62% -mode 3: 36% ... and when you measure again, it's like -mode 1: 84% -mode 2: 25% -mode 3: 4% ... Because as time moved, the string looked more like it was in one of those modes, as it was oscillating. But it quickly changed, as waves are always changing, when existing through time.
At 12:30, the measurement of energy makes a lot of sense aswell. Because that portion of the rope was moving/vibrating the faster (with more energy), as it kept going up and down so much. So that portion has the most energy, and the other portions near the edge, that didn't move much, don't have much energy in them. Right?
At 12:56, the measurement of position would just be taking where the electron is in the wave, right? So as the wave vibrates, the electron tries it's best to follow it, every now and then changing positions with other electrons in the system. Or maybe if it's alone in there, just trying it's best to fit the demand for electrons, but never quite managing to do it.
14:03 and again, as the wave was all chaotic, some of the energy was going up, some of it was going down, evenly. Just there were so many modes in action, it looked very chaotic as each and every one of them had an influence on the way the wave was going to look.
I honestly have no idea what I'm talking about, but it just feels like the particle and the wave are separate things, and the particle really likes being pushed around by the wave, which in turn is just a ripple in the fabric of space-time.
That's the best explanation of QP to the layman that I ever heard. Plus, I'm a game dev so I know matrices and vectors quite well. Now I want to understand how it relates to Eigen vectors.
Hi, David. Thanks for the kind words. In terms of the links to matrices, vectors etc... see Chapter 6 of The Quantum World notes available via the blog post linked in the video information. I'll be uploading videos on matrix mechanics for The Quantum World module in a few weeks. Philip (Moriarty, speaking in video)
@@thequantumworld6960 Wonderful, thank you so much. I've subbed to your channel. I was thinking about this last night, if you want to scale a basis matrix with a vector then eigenvectors are the way to go. How these would occur in nature is a total mystery to me though. I look forward to finding out!
14:18 If you relate it to stringed instruments. When you take the 'reading', is that the equivalent of trying to catch/pinch the string wave itself? So you stop the string vibrating and so the reading is off? Or, is taking the reading the equivalent of creating a harmonic on the string (caused by the lightest pressure on the string). And so the reading 'changes'? Its all very confusing :)
It depends on which reading you take! If you want to measure the energy of the string, you'll collapse it into a stationary state -- no movement, no oscillation, i.e. no sound... If you want to measure the position, you'll cause the waveform on the string to be a superposition of very many harmonics...which will all evolve (sometimes very quickly) in time. If you want to measure momentum, you'll again collapse the waveform to a superposition of harmonics...which will all evolve in time. See the simulation at the bottom of the blog post linked in the video information. And, yes, it is confusing. But, with practice, it becomes less confusing and the elegance and logic of QM starts to resonate... Philip (Moriarty, speaking in video)
Interviews with Prof Moriarty are my favourite. Not only nice and lucid explanations but also a pinch of humour: "That's B... - Rubbish? - Rubbish!" :D
I did a couple of weeks of quantum computing bare essentials in one of my classes for my CS degree 10+ years ago. Most of what I remember are the two superposed vector-states of the qubits rotating around a lot on the complex plane. All the rest of it faded into the ether.
Thank you so much!!! This in my opinion the one and definitive explanation about quantum mechanics which makes sense. It should be always explained this way in schools and in scientific publications for media. I’m a failed phisics student in 80’s and the main reason I quitted studying was the unbearable lack of connection between the models and how things work in the real world. Or at least it was how professors made it feel to me. Maybe I should have chosen engineering? 🤣
I never realised that, as a slightly nerdy musician, all I needed to understand quantum theory was a slightly nerdy musician to explain it. Thanks fo that! 😁
My physic teacher in high school said: Learning quantum mechanics is if you totally understand the lecture, you ain’t learn a thing. The real learning happen when question all the physics you have learned. I think I’m getting there.
I think Nigel Tufnel was onto something quantum when he said said D minor is saddest of all keys. "Just simple lines, intertwining." A superposition of Mozart and Bach... Mach!
Ohhh, nice! Thanks for that. Having written a book called "When The Uncertainty Principle Goes To 11", you'll understand why I particularly like your comment! Philip (Moriarty, speaking in video)
@@thequantumworld6960 This is also why Nigel doesn't want anyone to point at or look at his guitars. This act of observation would cause wave function collapse and ruin the famous sustain!
Haha, at 2:08, Quantum/Matrix/Particle Mechanics and Wave Mechanics are not *equivalent!* If they were equal, then why would Schrodinger make fun of Max Born's rule with his cat analogy? How is Max Born's "probability wave" equivalent to a wave of negative charge medium (electron medium) of Schrodinger's wave mechanics?
Nope, they're entirely equivalent -- it's largely a matter of personal preference, mathematical elegance and/or efficiency, and/or ease of visualisation whether you want to work with one or the other. Overlap integral or inner product? The choice is yours. See Chapter 6 of The Quantum World notes linked in the blog post given in the video information for more. See the other chapters for the answers to your other questions. Philip (Moriarty, speaking in video)
@@thequantumworld6960 ** Philip, thanks but Schrodinger's Wave Mechanics has no "wave function collapse", no probabilities, and does not deal with "point mass" or ray paths, like Matrix/Quantum Mechanics. Schrodinger's Cat idea exists, because they are opposite, physical theories! Quantum Particles collide and bounce/scatter, which is the reason for Max Born's rule, and Waves pass through each other when they collide. These are opposite physical theories, but sure Matrix Mechanic math and Schrodinger's equation have mathematical equivalency, as per Schrodinger's 1926 paper on the subject, "On the Relation between the Quantum Mechanics of Heisenberg, Born and Jordan, and that of Schrodinger."
@@thequantumworld6960 ** Lol Philip.. Nice, just shut up and calculate, right? But, forget about the physical reality of the computer that we are trying to build!
@@itsbs Of course it's not a question of shut up and calculate -- you're shifting the goalposts! Your argument was that matrix and wave mechanics were different formulations. My point was that they're equivalent in terms of their predictions. Therefore we choose the best tool for the particular job we're trying to do. That's all. Calm down. I've had my fill of arguing pointlessly on the internet so you're absolutely welcome to the last word on this, if that's what makes you happy.
An interesting metaphor for superposition is two tuning forks of the same frequency. If you strike the two forks with the same frequency you get one tone the two are indistinguishable and you hear one sound. If you vary the frequency of one you start to hear beat frequencies. It is interesting how with the same frequency it is like superposition well and is superposition. When the frequencies vary you start to get beat frequencies that correspond to decoherence into specific energetic states similar in some respects to spectral lines.
Thank you! This is the most interesting video on TH-cam. I keep rewinding again and again trying to understand this. I think I got understood some small bits 🙂❤️
People would be much less confused about quantum mechanics if they started with this video, instead of any other one. Thinking about waves that behave a bit weirdly when we interact with them (ie "observe") makes way more sense than thinking about mysterious particles that can jump randomly and instantaneously anywhere, and be at multiple locations at once.
I dont have a background in physics, so genuine question - you said there's an infinite number of harmonic waves. Given that a plank length is a thing, wouldn't that inherently make the amount of harmonic waves between 2 points finite?
I believe it's a common misconception that the plank length represents the spatial "resolution" of the universe, and that we know for certain nothing can vibrate smaller than that. Rather, our physics simply doesn't have the tools currently to describe what happens when things get down that small, so there very well could be harmonics that can vibrate small than the plank length, we just can't really describe them adequately yet
Is measurement speed an issue here? For example: if I take a picture of a vibrating string with a camera I'll end up with a blurry image of the average motion that occurred while the shutter was open. As I use faster cameras, the blur reduces and the state of the string becomes more exact. So I'm wondering how or if that factors into Quantum Mechanics.
It seems somewhat analogous to the Uncertainty Principle. If you take a fast photograph, you’re very certain of the string’s position, but it’s momentum is unknown, but with the blurry picture, the position is smeared out, but because you know how long your shutter is open for, you could figure out the momentum. I’m sure the analogy breaks down, but it’s an interesting observation.
The word 'measurement' is a little bit confusing. In your example, you're never actually measuring the string, not in the QM sense of the word. The camera is only measuring light that's being reflecting off of the string. It's indirect. To actually measure a waveform in the QM sense of measuring, you have to *interact* with it in some way, and that interaction is when the superposition collapses down to a single possibility.
I believe there would still be limitations from uncertainty. For instance, if you had a perfect picture (a literal instant) of a vibratin string you wuoldn't see ANY motion what so ever. You could see the amplitude at that exact moment, but you couldn't be sure if that was the maximum amplitude.
@@chipacabra Should I take that to mean the measurements in QM are effectively instantaneous and don't/can't suffer from a speed issue? In that the thing being measured doesn't change faster than the thing doing the measuring? Or perhaps more simply that it'll be hard for me to understand as a layman 😁.
The first reply is likely more adequate to your question. But I think that this particular example wouldn't help you enough for you to glimpse the measurement problem, like the others comments are discussing.
In your web app it shows that over time the sequence reverses and repeats. Is this the same in reality, or does the signal increasingly become more unstable?
Brilliant question. This is known as quantum revival. See the more technical post, "The Particle In A Box Is Not Simple", to which I link in the post included in the video information. Philip (Moriarty, speaking in video)
In audio plugins there is something called the Niquist frequency which is half the sample rate. If the sample rate is 48kbps, it can reproduce a sign wave at 24 thousand oscillations per second. If harmonics hit that frequency, they bounce back and create the most fascinating patterns in an undesirable and audible effect called aliasing. It's why analogue equipment is still used, because it does not produce this effect. "oversampling" (momentarily increasing the sample rate by a multiple of 2, 4 or 8 etc) can be implemented to mitigate the effect. interesting how similar this looks to aliasing.
This is a great video on quantum computing, so much of it is filled with the same hogwash we see in quantum mechanics of quotes of consciousnesses collapsing waves etc. An expertly concise way of explaining how it is possible to utilize the wave. Always love some Moriarty.
Imagine how mad would you get trying to put your quantum password in a quantum cryptographic password system and failing to login because your password only has a higher probability of being correct.
One slight correction - the attack is much more important than the set of harmonics for distinguishing sounds that come from different instruments. This was shown by the "cut bell" experiments of Pierre Schaeffer
The "particle" is a superposition of waves. Each of those waves has its own spatial frequency, and therefore is associated with a different kinetic energy, and thus travels with a different speed. This means that the wavepacket that describes the particle disperses so that it breaks up into its component waves -- you're seeing waves travelling at different speeds hit the wall and get reflected. See Chapter 3 of the Quantum World notes available via the blog linked in the video information above. Philip (Moriarty, speaking in video)
When I see Dr. Moriarty in the thumbnail I know I'm going to watch. Another excellent explanation, of course. Is the monkey going to be featured in more videos? He was capable demonstration assistant.
@@ekstrapolatoraproksymujacy412 It's also exactly 1/3rd of a string relative to 1/1 of a string, 7th fret on the guitar is a fifth relative to 0th fret, it's the same relative to the 2nd mode tho, because the 2nd mode is just the octave!
It decides when it’s being measured because it is part of a conscious fabric. It very well could be neutrinos and the positive and negative occurrences from it that hold the key
I'm not an expert on any of this but I am still convinced the universe is a bunch of little electro-magnetic bubbles wobbling around one another with a different level of surface tension that allows a viscosity causing solid and semi-solid objects. The more these bubbles nestle themselves into one another's "cracks" or fields the higher the density and the stronger the object.
I think this deserves a continuation to explain how quantum computing really computes.
came here to say the same. we need round two! how do you go from the superpositioned waves to an actual computation?
@@ByteMe1980 I came here to say the same thing too!
He kinda said he didn't know in the video. He said he isn't part of it but there are people working on algorithms to try and use these superpositions as waves.
5km view just to see how it looks like. With the factorization as example (Shor algorithm)... You enter the 2 numbers as wave "periods", once collapsed it will give you the "period" of when the two combined numbers are the same, which is the factor.
Imagine 2 gears with different numbers of teeth, the common factor will be the turns you have to do so both gears are at the same position as the start.
A classical computer hast to count the turns until it repeats. A quantum computer does it "instantly".
Of course "enter" and "give" involves a lot of math and calculations, but basically all the computation is done by manipulating wave properties in a clever way.
@@ByteMe1980 The basic idea of (some) quantum computing is that you expand the state of the qubits into a particular superposition, apply some algorithm, and then carefully undo the initial expansion with some inversion operation so that you measure something with certainty (or near certainty in many cases). Now, as Phil says at the start, it can be mischaracterised if you're not careful, as there's nothing magic about this (the way you set up the quantum state is very precise), and very often the superposition you set up does not have some trivial one-to-one correspondence with the values of classical bits as is typically descibed, but I wouldn't say it's far off.
5:53 'I don't have infinite energy'
Your videos suggest otherwise, Phil
We're fighting the second law but we aren't winning.
There's only just so many After Eight mints in that box, Eline.
He has a way of explaining something in a way that makes it relatively easy and impossible to understand at the same time. I mean it as a compliment.
So you are basically in a super position of eureka and total confusion at the same time.
@@3dlabs99 Yes, exactly. Only thing left to figure out is how to get a nobel prize out of this situation.
I followed and lost it and still stayed with him.
I very much take this as a compliment! Thank you so much. Contrary to popular belief, confusion is not necessarily something to be avoided in teaching. See the blog post linked in the video information.
Philip (Moriarty, speaking in video)
Then maybe you don't realize what you said. If the student hasn't learned...
What I appreciate most about prof Moriarty is that he's so vocal about science not knowing - and how that doesn't matter for the science. Why? We don't know. Period. We may know one day, but then there's likely to be more stuff underneath or within that we don't know - science rarely runs out of questions, but we learn more all the time.
Well said!
I find it similar to how you can still do useful work with a car even if you don’t know how it works. You can still drive it and carry stuff. If you take the time to learn how it works, you can manipulate it to be more efficient or effective, or to build new cars that are better suited for specific tasks.
Even if you don’t know why the wave collapses to one of those states, you can still exploit its properties to do useful work.
How has Holmes not captured Moriarty, right there in Nottingham?
Science is art of finding relevant questions.
That slinky demonstration is the best example I've seen to explain harmonics in the string! Thank you! I was not expecting timbre to be related to quantum computing
It would also be a really simple way of showing how the energy in a photon is proportional to the wavelength. Hopefully some middle school teacher steals it.
@@t_ylr that's an amazing connection to make.
Can light waves have a similar "timbre"? Can you somehow add light waves of different frequencies together?
@@ButchMarshall Absolutely. In fact, *all* real light waves have a spread of frequency. It might be very, very, very narrow but the only time we have a pure frequency (i.e. a single value that is defined right down to an arbitrary number of decimal places) is for a wave that lasts an infinite amount of time (or spreads across an infinite amount of space) without being disturbed. But this is a mathematical idealisation....
Philip (Moriarty, speaking in video)
@@thequantumworld6960 so what stops us from making qubits using lasers and measuring device? Why the need for these superconducting super chilled interfaces into the qubit?
@@ButchMarshall It's likely a lot easier to control electrons than photons. They're computing with the bits, you have to find ways to perform operations on them and I'm guessing it's a lot easier to do that with electrons. If anyone has any better ideas I'd like to know if there's a real answer.
Every time he says "Monke" I get the biggest smile on my face haha
Love ya Professor, keep it up!
"Quantum mechanics is simple: it's just wave interference and harmonics."
"So we can measure a quantum wave and all its harmonics?"
"No, you can't do that, it'll stop moving and lose all its harmonics."
"Why?"
"No one knows."
No we do know. Adding energy to the system, by shooting a photon at it or having it hit a detector collapses the harmonics into a single macro state. Like putting your finger on the bass string directly changes its timbre.
@@ac.creations That's not explaining what happens though, that is just an explanation of what can cause a collapse, but not what happens during the collapse.
There are two theories.
Copenhagen Interpretation: The waveform instantly collapses into one state upon observation.
Many-Worlds Interpretation: The waveform never collapses. Upon observing, the observer becomes "entangled" with the waveform, meaning that both the original waveform and the observer's waveform are in one big superposition. The waveform looks like it collapses to you because you are now part of it.
@@samuelthecamel Why does that lead to "many worlds"? Ok, so I'm entangled with a waveform, why does that make the universe split (I know that's not accurate terminology, maybe "branch" is better)?
Neither of these approaches explain why this happens, only what happens
This is hands down the best video I ever watched on Quantum Mechanics, and I’ve watched a fair few. I love how Phil isn’t afraid to use analogies, but also tells us where the limits of the analogy are, and his dedication to being accurate even in his layman’s explanations reminds me of Richard Feynman’s approach.
Precisely! It's both simple and intuitive while not shying away from the big picture. Vey Feynman-like Indeed. Takes a lot of skill to come up with explanations like that. I wish I had that kind of talent. I tend to complicate things more when I try though.
Agreed. It's the first time I have seen an explanation of superposition that actually made sense :D
I love how scientists get so excited when they say “I don’t know”
"If you can answer that question, you get a Nobel Prize."
That's a pretty funny answer to the question "Why?" about a part of quantum physics that does confuse people.
@@ZT1ST Of course it confuses people. It confuses physicists too! The measurement problem is unresolved. Would you prefer that I made up some explanation or pretend that parallel universes are the answer (on the basis of zero empirical evidence)?
Philip (Moriarty, speaking in video)
"I don't know... yet" is like job security or printing money to scientists. Really plays into that part of our lizard brains that likes random chance, like what if we find out and it's really valuable.
Just to make it sound a little less noble, a little more real.
That's fair enough though. Scientists LIVE for the day they can find out what they don't know, its almost as great as when you actually figure it out :D
@@CaptainWumbo
I whish this was true...but the reality is not a lot of money is lining up to fund research where the answer is "I don't know" to the question "How will this be valuable"
Insanely good video, on of the best of prof Moriarty! I never heard QM being condensed into such a simple and intuitive explanation.
I've learned more about Quantum Computing and Quantum Mechanics from a few computer file videos with Professor Phil Moriarty than I have from a lifetime of 'documentaries' and hyperbolic articles. His ability to elucidate and cut through the bull is fantastic. Genuinely appreciate his enthusiastic but humble approach to communicating traditionally mystified topics.
This is incredibly easier to understand than before. Thank you for being well versed.
Finally someone who does not resort to saying "..some magic happens...and presto...".
I learned something today. Thank you mr. Moriarty.
Fantastic use of Bass to explain superposition. Davie504 would be proud of you.
He wrote a whole book on that :) Turn up to eleven!
Everyone needs to SLAP the like button on this video ;)
As a former jazz pianist with excellent ear but no background in science, this video makes perfect sense. If you play a low bass note on a piano, you can hear almost as much mid and treble as you can hear bass, and if you listen carefully you can hear all the harmonic notes in the sequence, but everything must all balance out to being most 'probably' (definitely) the note that it is.
Finally a legit explanation on the topic of quantum physics, and not some garbage pushed by journalists who don't have a clue. Thank you so much!
I understood that from my experiments in audio DSP. This gives me the courage to think that if I delve deeper into this I may actually understand more. It's the first time I ever imagined that I might grasp what this is all about.
I have always loved this guy's passion and overall demeanor when he talks about his field of science.
He gets me pumped up when he gets so excited and passionate about whatever he's talking about.
At 7:36, if Quantum Computers compute via wave interference, why aren't they just considered classical, analog computers? Wave interference is a very classical physics phenomenon being used for computing. You say the word "states", but does that just mean the analog, waveform shape at a particular time?
At 8:57, is a "Quantum" explanation, but it seems that the classical, analog waveform being measure is a resonance *"state"* (or one of the overtones). Again, this still seems very classical. In terms of "Quantumness," is it because we just don't know which resonance *"state"* will be measured?
Sincerely, I think this is the thing missing in this video. - a clearer explanation of how quantum computing computes.
For what I understood the quantum computation comes nt from "waveform shape at a particular time" but the multiple combinations of the various single"waveform shapes at a particular time". That is why he reject the notion that quantum is the result of infinite computation.
The best I could grasp is that quantum computing aggregates the probabilist result of the many variation of the waves a particle - qubit - can generate from a given input.
Again, I mgiht be wrong, but whan Ive saw explained differently, the difference from clasical computing is that the output is either 0-1. In quantum the result comes in terms of probabilites: from all the positions that the wave represeting this qubit uccupied uring the calculation, which is the most probable output.
The benefit apparently comes from the fact that you can do with one qubit the calculations one could do with many bits.
@@mustavogaia2655 **
This would be like an analog computer that used overtone/harmonics of a fundamental wave to do computing.
**
But, if you get these random energy peaks or random position peaks when you measure the wave, can you build a computer based off of random number generation? i.e. qubits seem to just produce a random number when measured.
@@itsbs
Yes, but this would be considered a single quantum operation.
Again, not an expert, but the "peaks" are dependent on the function/matrix the is passed thru.
@@mustavogaia2655 **
I thought he just said "when measured" you get some different (maybe random) waveform.
What you neglected to explain is what exactly is special about quantum computing.
If we could do those calculations on any wave system - there are much easier ways to do it from pendulum systems to vibrating strings. But we don't see guitar calculators - so there is something special about quantum that allows certain types of parallel algorythms to work incredibly fast.
i definitely understood it better than EVER before! is like polyphonic singing or overtone singing. treating particles as voice, they have many overtones but when meassured (meaning extracting energy from the particles to excite sensor and let it know there is something) the energy drops and falls into a single overtone. which will vibrate over time and make new multiple pletora of overtones again. soo cool!!!
Man I wish this video was longer. Would love to hear Phil go into more detail about this. Very interesting topic plus Phil is just the best.
*Prof:* If I pick up the base [...]
*Davie504:* He must be *_D E S T R O Y E D_*
As someone who is confused by many videos on quantum mechanics etc I found this helpful but I wish it had gone further. How can we derive a one or zero from a wave when making the measurement seem arbitrary? I don’t get it, he said over and over.
I think that was skipped because the answer can be quite involved and mathsy. That's the weird part he alludes to, ie. the truly quantum part, rather than just superposition/wave mechanics. There's no reasonable analogy you can make from a quantum superposition collapsing to a guitar string oscillating. A qubit's superposition collapsing into either zero or one is pure quantum mechanics: energy levels turn out to be discrete, not continuous, so in this case it must pick one energy level or the other (which we label as zero or one) when we measure it, not somewhere in between. How that measurement actually physically works in a quantum computer I'm not sure, but there are lots of ways to disturb a quantum superposition and it happens all the time without our involvement.
On the maths side of things, most of the time we can't derive a one or a zero from a qubit's superposition with certainty, even if we have perfect knowledge of its state. We can only derive the _probability_ that a qubit will be zero or one when we measure it. What state it actually ends up in is random, based on that probability distribution (or at least, that's how it appears to us). The clever and difficult part of quantum algorithms is manipulating the qubits/superpositions so that they interact in such a way that they calculate something useful while also ensuring when we do a measurement we get the answer we want with certainty _or_ with high enough probability that if we run the algorithm a few times we end up with the right answer. Honestly, I only have a vague high level understanding of this because the nitty-gritty of how it works involves a lot of linear algebra. For a concrete example, minute physics has a great video on Shor's algorithm, and 3blue1brown has some very helpful explanations of the maths involved.
(context: I took a couple quantum computing units I didn't have enough time to understand in detail, so I'm far from an expert)
The ones and zeroes are measued with probabilities that are determined by the quantum algorithm. In an ideal scenario, the probability of measuring the correct result is 100%, but it usually isn't quite that simple.
It's a 15 minute video. You're not going to get a detailed, blow by blow analysis of quantum computing/quantum mechanics in 15 mins! I teach the first semester of our Quantum World module, which is 12 weeks of tuition, involving a total of 37 videos, eight worksheets, 12 in-person teaching sessions, and many other tutorial/exam/revision sessions...
...and still we barely scratch the surface of quantum mechanics. One key issue with TH-cam "edutainment" is the idea that complex, complicated questions have straight-forward answers that can be expressed in a clickbait video title. As Feynman said when asked to describe "in a few sentences" the work for which he won the Nobel Prize: "If I could explain it in a few sentences, I wouldn't have won the Nobel Prize."
The blog post linked in the video information (and the other posts/articles in turn linked in there) provide a lot more background and information. But the intellectual heavy lifting when it comes to understanding a subject like QM has to come from the learner, not the teacher.
Sorry for such a long reply but this is an aspect of TH-cam edutainment that particularly exercises me!
Philip (Moriarty, speaking in video)
@@thequantumworld6960 Really interesting to hear that first hand Philip. You and some of the others over at Sixty Symbols did a video years ago about the state of high school physics and the public perception of the subject... it would be interesting to hear more from you about what you think this big world of TH-cam physics/maths/science videos needs to be careful about and how one should go about getting the balance between detail and engagement correct.
Moriarty is the king when it comes to intuitive explanations.
I've seen most of the videos on TH-cam tying to explain what superposition is and this is by far the best explanation. Thank you so much!
This is the best explanation of quantum phenomena I have ever seen. Outstanding.
I'm emailing this video to my old quantum mechanics professor. Excellent explanation!!
Always such a pleasure seeing Professor Moriarty in action. I'm sure he could be reading his weekly shopping list and make it sound exciting...
At 12:23, when you make a measurement, are you just getting a random energy peak that doesn't match the original wave form? If you measure for position, you are getting another, seemingly random answer. Are Qubits just natural random number generators?
Yes!, but you do know all the possible outcomes or energy peaks you could get, you can then recreate (by repeating the same experiment a lot of times) the (probability) distribution of peaks that makes up your initial wave form.
And yes, there are experimental proposals of random number generators using qubits, for example using single photon generators and beam splitters.
@@Miguel_Noether **
So it is like you are random sampling a waveform. It still seems very classical, analog, so how can you make a computer out of this natural, randomized feature?
@@itsbs I don't think I could give you a general answer. You could look for the Grover algorithm which consists in looking for an item stored in a list. The key idea is that you let you quantum computer work on "these distribution of peaks". At the last moment when you do your measurement, the algorithm makes that distribution in such a way that if you do the experiment a lots of times you will almost in all cases get the state representing the item you are looking for.
The Grover algorithm also has a very geometric way to view how the computation works
@@Miguel_Noether As a lay person to quantum computing. Thats what I took from this video as well. First time I felt I had a rudimentary understanding of how the heck one works.
It also cemented the idea of why quantum computers are great for highly complex problems. And would be foolish to use for most things classical computers are currently doing for consumers. Why Phil points out how coding for quantum is a whole different subject.
If I follow the examples here. Classical logic gates perform a single function per cycle. Whereas quantum qbits can extract multiple (infinite?) data points per "cycle"? Its all dependent on how the coding of the quantum computer was structured. It sounds like coding a quantum computer is more difficult than making the computer itself.
I am a musician and using the harmonic series to explain this is perfect for me, thank you so much, I feel as if this video was almost made for me.
This video reminded me why I love physics so much. Reality can be quite trippy.
hands down my fav computerphile video of all time
This might be one of my favorite Moriarty videos yet. I feel like I've said this about basically every single one that came out before this, though 😅
As a layperson who's been curious and studying the subject casually for some time, this really feels like a great sweet spot between the whole "quantum is wooonky" and "quantum is just plain math" attitudes you see here and there.
Thank you for explaining that superposition does not mean "every possible position all at the same time." I have heard this description almost exclusively, and it never made sense to me. I chalked up the "doesn't make sense to me" as being inherent in the fact that it is quantum mechanics. While I, of course, don't understand quantum mechanics much better now than before... I do have a better handle on what questions I need to ask.
Sean and Phil: bravo for agreeing to tackle this complicated topic and doing or so well.
I'm glad I'm not the only one frustrated with all the "QC explained in 10 minutes" videos. They all can be summarised as "I'll restate the confusing part and pretend that's the explanation for it."
As a musician, I can know understand a representation of the concept of superposition. That was amazing Phil.
Not mentioned in video, but key to quantum computing is the ability to manipulate the probability of the collapsed wave function using microwave pulses. That's what quantum gates and circuits are for.
Yes, and hopefully we'll get to this in a future video. The entirety of quantum computing/quantum mechanics is not going to be explained in a 15 minute video...
Philip (Moriarty, speaking in video)
This is something I still wish to understand. From the start of learning about QC, I wondered what substituted the logic gates of classical computers with a device that can have countless states as output. Seems Im slowly getting there thanks to these and other videos.
I also have to think (I could easily be mistaken), we are currently coupling QC with classical ones, to make sense of the massive amount of information they generate?
Its easier (for me) to think of QC as standalone data output devices rather than a full blown computer unto itself? In a world were we have grown up around classical computers up till now. Seems nearly impossible to build a purely QC ground up with a user interface? I kinda think of it like a D/A A/D converter. QC into classical??? Then the obvious issue of needed bandwidth to pull this off. Dunno... Still trying to understand it all. Slowly but surely.
Little did I know I'd find the best explanation of the Measurement problem on a Computer channel
I had been struggling with understanding superposition until I watched this video. Thanks for making it very clear!
The course I took on acoustics gives me a little bit of a leg up on understanding this, as I knew precisely where Dr. Moriarty went with the accumulated sine waves expressing the timbre of the sound and how it applies to quantum computing. Imagine using the Fast Fourier Transform algorithm to assist in quantum computing. Very interesting video... hats off!
Great point! Fourier transforms are absolutely core to quantum mechanics (and therefore quantum computing.) See the blog post linked in the video information (and the links therein) for much, much more on Fourier's role in QM.
Philip (Moriarty, speaking in video)
Literal perfect timing, exactly the video i was looking for only uploaded hours ago :)
Incredible video. Incredible wealth of knowledge. You best believe I’ll be watching this multiple times
those were all amazing analogies that, except for one, i hadn't heard before, and that may be one of the best overall introductions to the subject i've heard. very fun.
Maybe the physics we call "classical" are just narrowly applicable on specific energy levels, which are the levels we exist at -- whereas most of the universe is either near absolute zero, or at extremely high energy levels. And when we "measure" something, we're just reducing the temporal dimension (an "instant" to us) to where it behaves like the everyday physics we are familiar with. Sort of like how an ocean would appear like a solid if you interacted with it at 0.01 frames per second -- but behaves like a wavy liquid at 100 frames per second.... if that makes sense
That's a great analogy
yeah that's very similar to my own pet theory of what's going on. If we consider time as we understand it to be the 4th dimension of our existence with things like how gravity can bend "spacetime" and whatnot, electrons at a quantum level could be thought of as existing at a dimensionality beyond our 4 intuitive dimensions. If we also add to this the concept that time exists at the finest level with a discrete smallest unit of time (there exists a unit of time that cannot be divided), the issue of "probability" in measurement could be that when we attempt to measure the electron in our limited 4 dimensions we are actually "collapsing" 5 or more dimensions into just 4 to get our measurement, thus why the wave collapses into a single state since our action of measuring in 4 dimensions causes us to "hold constant" any other dimensions at play, thus destroying the harmonic (take a 2 dimensional wave-form, and force it into 1 dimension to take a measurement, you can't return now to the original 2 dimensional state) -- Wish I knew enough to work out this theory a little further, it's very interesting to think about.
I like that. Problems like this (I believe) probably depends heavily on relatively and our 3 dimensional observations. The energy levels we're used to interacting with also coexist with the only life (that we know of) in our small sliver of the universe..... so how do we know gravity doesn't bias our answers? The universe as we know it is mostly empty space, and we happen to be conducting all of our experiments really close to a fairly large mass, which as we know has an effect on our perception of time... Think about this, if a small object (baseball) is released next to another object with significantly greater mass (planet), the ball will appear to be getting closer to the planet (relative to the planet) and the planet will appear to be getting closer to the ball (relative to the ball), yet an outside observer will clearly see the ball moving towards the planet (the right answer?) The fact that there's 3 different conclusive answers to this one measurement isn't weird, it's relativity, but what happens if you can't become the third observer? How do we even know when we are the third observer when measuring something? Can you prove when we are?
Loved this! I have never heard this kind of explanation of Quantum Computing before.
Nice to see someone aging right along with me.
I felt this in my bones.
rip
Very nicely done, and now you're playing bass, love it! Fantastic explanation along with your fantastic book! Thank you so much.
This is the best video of quantum mechanics ever!
The only ones who've ever attempted to describe how D-wave works are D-wave themselves, last time I checked. I've never been convinced by their explanations that what they're doing actually "works" and I've never seen an application for what their systems might be able to do for a business, certainly not versus a cost analysis.
Does Professor Moriarty have his own TH-cam channel? I'd be interested in seeing some longer form content from him. I always enjoy the videos with him in them.
I'm also curious
I think he does but can't find it.
Hi, @PBJ AND A HIGHFIVE.
Thanks so much for asking. Yes, I have a channel, "The Quantum World", which features videos for our 2nd year undergraduate physics course of the same name. Click on the avatar...
Philip (Moriarty, speaking in video)
@@thequantumworld6960 I'm glad you checked the comments and responded! Just subscribed.
The university could find a way to publish his lectures like MIT is currently doing in their channel.
I enjoyed the video a lot! He is clearly enjoying the video-class and the topic! This are the kind of teacher that inspire students!
"Computer scientist really like their matrices and vectors"
Oh, finally an explanation that ill unders- nope its music
...but it's all the same! Wave mechanics and matrix mechanics are the same principles, just expressed in a different "language". A function can be thought of as a vector in a high dimensional space...
Philip (Moriarty, speaking in video)
I think I finally ... well, not get it, but, I'm pretty sure this is the closest to understanding how I should be thinking about the concept so far. Excellent video. Again professor Moriarty is inspiring me to use my uneducated software developer brain to really get my head around computer science, maths and physics. Thank you
This is so relatable. Best explanation of quantum computing ever!
At 9:32, when porting the guitar string analogy, why wouldn't you use Schrodinger's Wave Mechanics? In other words, apply Schrodinger's explanation of "charge density" of the electron medium energy that you are detecting, instead of thinking about it as the probability of detecting an individual ball/sphere electron particle?
Both describe the same thing, the difference lies on how you would like to interpret the results
@@Miguel_Noether **
I see them opposites... like water in a lake (medium) versus a billiard ball (particle). When particles collide, they bounce and scatter. When waves in a medium collide, the pass right through each other. Opposites...
At 9:15, I thought the answer was going to be something like:
-Just like the string of the bass, if you take a picture of the string vibrating (you measure it), your measurement is going to be standing still in time (pictures don't move) and as such, the string is going to look like it is in one of those states (more to one than the others), but if you measure it again, it may look more like another state now (as the string continued to vibrate before you took another picture).
So... the reason the measurements are in a random superposition, is because the wave is vibrating, through time. But when you measure it, your measurement is standing still in time, and is a mere snapshot of where it was at a random point in time. Waves exist through time; measurements stand still.
You could make a metaphor of trying to take a frame out of a movie. It's all blurry because there is no time element. No wave; just a measurement.
The wave collapses into one of the states because measuring means taking the element of "time" out of the system.
Does that make sense or am I missing something?
Pardon my bad English. Feel free to correct me anytime.
Also, let's say you have infinite modes of vibration (as in 5:20).
Your measurement would be like a list of probabilities, right?
-mode 1: 8%
-mode 2: 62%
-mode 3: 36%
...
and when you measure again, it's like
-mode 1: 84%
-mode 2: 25%
-mode 3: 4%
...
Because as time moved, the string looked more like it was in one of those modes, as it was oscillating.
But it quickly changed, as waves are always changing, when existing through time.
At 12:30, the measurement of energy makes a lot of sense aswell. Because that portion of the rope was moving/vibrating the faster (with more energy), as it kept going up and down so much.
So that portion has the most energy, and the other portions near the edge, that didn't move much, don't have much energy in them.
Right?
At 12:56, the measurement of position would just be taking where the electron is in the wave, right?
So as the wave vibrates, the electron tries it's best to follow it, every now and then changing positions with other electrons in the system.
Or maybe if it's alone in there, just trying it's best to fit the demand for electrons, but never quite managing to do it.
14:03 and again, as the wave was all chaotic, some of the energy was going up, some of it was going down, evenly. Just there were so many modes in action, it looked very chaotic as each and every one of them had an influence on the way the wave was going to look.
I honestly have no idea what I'm talking about, but it just feels like the particle and the wave are separate things, and the particle really likes being pushed around by the wave, which in turn is just a ripple in the fabric of space-time.
That's the best explanation of QP to the layman that I ever heard. Plus, I'm a game dev so I know matrices and vectors quite well. Now I want to understand how it relates to Eigen vectors.
Hi, David.
Thanks for the kind words. In terms of the links to matrices, vectors etc... see Chapter 6 of The Quantum World notes available via the blog post linked in the video information. I'll be uploading videos on matrix mechanics for The Quantum World module in a few weeks.
Philip (Moriarty, speaking in video)
@@thequantumworld6960 Wonderful, thank you so much. I've subbed to your channel. I was thinking about this last night, if you want to scale a basis matrix with a vector then eigenvectors are the way to go. How these would occur in nature is a total mystery to me though. I look forward to finding out!
What an excellent description. Well done.
14:18
If you relate it to stringed instruments. When you take the 'reading', is that the equivalent of trying to catch/pinch the string wave itself? So you stop the string vibrating and so the reading is off?
Or, is taking the reading the equivalent of creating a harmonic on the string (caused by the lightest pressure on the string). And so the reading 'changes'?
Its all very confusing :)
It depends on which reading you take!
If you want to measure the energy of the string, you'll collapse it into a stationary state -- no movement, no oscillation, i.e. no sound...
If you want to measure the position, you'll cause the waveform on the string to be a superposition of very many harmonics...which will all evolve (sometimes very quickly) in time.
If you want to measure momentum, you'll again collapse the waveform to a superposition of harmonics...which will all evolve in time.
See the simulation at the bottom of the blog post linked in the video information.
And, yes, it is confusing. But, with practice, it becomes less confusing and the elegance and logic of QM starts to resonate...
Philip (Moriarty, speaking in video)
"This is one Hertz ... this is two Hertz ... this REALLY hurts"
Those PC speakers should be in an archaeological museum. 10:10
I know! I love 'em!
Philip (Moriarty, speaking in video and owner of said speakers)
Interviews with Prof Moriarty are my favourite. Not only nice and lucid explanations but also a pinch of humour: "That's B... - Rubbish? - Rubbish!" :D
I did a couple of weeks of quantum computing bare essentials in one of my classes for my CS degree 10+ years ago. Most of what I remember are the two superposed vector-states of the qubits rotating around a lot on the complex plane. All the rest of it faded into the ether.
15:12
Quantum Physicist: What's your trajectory?
Wave: Yes
Davie504 would approve of this method of explanation.
This is the best video on the internet
That was probably the closest that I've ever been to nearly grasping the concept of quantum mechanics.
Professor Moriarty is so good at explaining this stuff.
Thank you so much!!! This in my opinion the one and definitive explanation about quantum mechanics which makes sense. It should be always explained this way in schools and in scientific publications for media. I’m a failed phisics student in 80’s and the main reason I quitted studying was the unbearable lack of connection between the models and how things work in the real world. Or at least it was how professors made it feel to me. Maybe I should have chosen engineering? 🤣
I never realised that, as a slightly nerdy musician, all I needed to understand quantum theory was a slightly nerdy musician to explain it. Thanks fo that! 😁
My physic teacher in high school said: Learning quantum mechanics is if you totally understand the lecture, you ain’t learn a thing. The real learning happen when question all the physics you have learned. I think I’m getting there.
I think Nigel Tufnel was onto something quantum when he said said D minor is saddest of all keys. "Just simple lines, intertwining." A superposition of Mozart and Bach... Mach!
Ohhh, nice! Thanks for that. Having written a book called "When The Uncertainty Principle Goes To 11", you'll understand why I particularly like your comment!
Philip (Moriarty, speaking in video)
@@thequantumworld6960 This is also why Nigel doesn't want anyone to point at or look at his guitars. This act of observation would cause wave function collapse and ruin the famous sustain!
Love that we can see his music hobby on display; bass, amp, mike
Haha, at 2:08, Quantum/Matrix/Particle Mechanics and Wave Mechanics are not *equivalent!* If they were equal, then why would Schrodinger make fun of Max Born's rule with his cat analogy? How is Max Born's "probability wave" equivalent to a wave of negative charge medium (electron medium) of Schrodinger's wave mechanics?
Nope, they're entirely equivalent -- it's largely a matter of personal preference, mathematical elegance and/or efficiency, and/or ease of visualisation whether you want to work with one or the other. Overlap integral or inner product? The choice is yours. See Chapter 6 of The Quantum World notes linked in the blog post given in the video information for more. See the other chapters for the answers to your other questions.
Philip (Moriarty, speaking in video)
@@thequantumworld6960 **
Philip, thanks but Schrodinger's Wave Mechanics has no "wave function collapse", no probabilities, and does not deal with "point mass" or ray paths, like Matrix/Quantum Mechanics. Schrodinger's Cat idea exists, because they are opposite, physical theories! Quantum Particles collide and bounce/scatter, which is the reason for Max Born's rule, and Waves pass through each other when they collide. These are opposite physical theories, but sure Matrix Mechanic math and Schrodinger's equation have mathematical equivalency, as per Schrodinger's 1926 paper on the subject, "On the Relation between the Quantum Mechanics of Heisenberg, Born and Jordan, and that of Schrodinger."
@@itsbs "... but sure Matrix Mechanic math and Schrodinger's equation have mathematical equivalency"
Exactly my point. Thanks for confirming.
Philip
@@thequantumworld6960 **
Lol Philip.. Nice, just shut up and calculate, right? But, forget about the physical reality of the computer that we are trying to build!
@@itsbs Of course it's not a question of shut up and calculate -- you're shifting the goalposts! Your argument was that matrix and wave mechanics were different formulations. My point was that they're equivalent in terms of their predictions. Therefore we choose the best tool for the particular job we're trying to do. That's all. Calm down. I've had my fill of arguing pointlessly on the internet so you're absolutely welcome to the last word on this, if that's what makes you happy.
Love to see professor Moriarty, very down to earth
An interesting metaphor for superposition is two tuning forks of the same frequency. If you strike the two forks with the same frequency you get one tone the two are indistinguishable and you hear one sound. If you vary the frequency of one you start to hear beat frequencies. It is interesting how with the same frequency it is like superposition well and is superposition. When the frequencies vary you start to get beat frequencies that correspond to decoherence into specific energetic states similar in some respects to spectral lines.
Thank you! This is the most interesting video on TH-cam. I keep rewinding again and again trying to understand this. I think I got understood some small bits 🙂❤️
People would be much less confused about quantum mechanics if they started with this video, instead of any other one. Thinking about waves that behave a bit weirdly when we interact with them (ie "observe") makes way more sense than thinking about mysterious particles that can jump randomly and instantaneously anywhere, and be at multiple locations at once.
I dont have a background in physics, so genuine question - you said there's an infinite number of harmonic waves. Given that a plank length is a thing, wouldn't that inherently make the amount of harmonic waves between 2 points finite?
I believe it's a common misconception that the plank length represents the spatial "resolution" of the universe, and that we know for certain nothing can vibrate smaller than that. Rather, our physics simply doesn't have the tools currently to describe what happens when things get down that small, so there very well could be harmonics that can vibrate small than the plank length, we just can't really describe them adequately yet
Is measurement speed an issue here? For example: if I take a picture of a vibrating string with a camera I'll end up with a blurry image of the average motion that occurred while the shutter was open. As I use faster cameras, the blur reduces and the state of the string becomes more exact. So I'm wondering how or if that factors into Quantum Mechanics.
It seems somewhat analogous to the Uncertainty Principle. If you take a fast photograph, you’re very certain of the string’s position, but it’s momentum is unknown, but with the blurry picture, the position is smeared out, but because you know how long your shutter is open for, you could figure out the momentum. I’m sure the analogy breaks down, but it’s an interesting observation.
The word 'measurement' is a little bit confusing. In your example, you're never actually measuring the string, not in the QM sense of the word. The camera is only measuring light that's being reflecting off of the string. It's indirect. To actually measure a waveform in the QM sense of measuring, you have to *interact* with it in some way, and that interaction is when the superposition collapses down to a single possibility.
I believe there would still be limitations from uncertainty. For instance, if you had a perfect picture (a literal instant) of a vibratin string you wuoldn't see ANY motion what so ever. You could see the amplitude at that exact moment, but you couldn't be sure if that was the maximum amplitude.
@@chipacabra Should I take that to mean the measurements in QM are effectively instantaneous and don't/can't suffer from a speed issue? In that the thing being measured doesn't change faster than the thing doing the measuring?
Or perhaps more simply that it'll be hard for me to understand as a layman 😁.
The first reply is likely more adequate to your question. But I think that this particular example wouldn't help you enough for you to glimpse the measurement problem, like the others comments are discussing.
This video is a fantastic explanation of quantum systems!
"I won't be able to explain it in 10 minutes." Proceeds to explain it in 15
In your web app it shows that over time the sequence reverses and repeats. Is this the same in reality, or does the signal increasingly become more unstable?
Brilliant question. This is known as quantum revival. See the more technical post, "The Particle In A Box Is Not Simple", to which I link in the post included in the video information.
Philip (Moriarty, speaking in video)
8:17 This reminds me of old analog computers.
11:15 Adding waves?
In audio plugins there is something called the Niquist frequency which is half the sample rate. If the sample rate is 48kbps, it can reproduce a sign wave at 24 thousand oscillations per second. If harmonics hit that frequency, they bounce back and create the most fascinating patterns in an undesirable and audible effect called aliasing. It's why analogue equipment is still used, because it does not produce this effect. "oversampling" (momentarily increasing the sample rate by a multiple of 2, 4 or 8 etc) can be implemented to mitigate the effect. interesting how similar this looks to aliasing.
Perhaps hands down the best description of quantum mechanics, suddenly it makes sense!
This is a great video on quantum computing, so much of it is filled with the same hogwash we see in quantum mechanics of quotes of consciousnesses collapsing waves etc.
An expertly concise way of explaining how it is possible to utilize the wave. Always love some Moriarty.
Great insight Phil, please keep them coming !
That made that topic a lot clearer, Thank You
Imagine how mad would you get trying to put your quantum password in a quantum cryptographic password system and failing to login because your password only has a higher probability of being correct.
One slight correction - the attack is much more important than the set of harmonics for distinguishing sounds that come from different instruments. This was shown by the "cut bell" experiments of Pierre Schaeffer
When "it" hits the walls at 13:40, what determines the frequency that arises there?
The "particle" is a superposition of waves. Each of those waves has its own spatial frequency, and therefore is associated with a different kinetic energy, and thus travels with a different speed. This means that the wavepacket that describes the particle disperses so that it breaks up into its component waves -- you're seeing waves travelling at different speeds hit the wall and get reflected.
See Chapter 3 of the Quantum World notes available via the blog linked in the video information above.
Philip (Moriarty, speaking in video)
wait. is the waveform presented around 12:20 like a continuous probability distribution..?
When I see Dr. Moriarty in the thumbnail I know I'm going to watch. Another excellent explanation, of course.
Is the monkey going to be featured in more videos? He was capable demonstration assistant.
The 3rd Mode is exactly a musical fifth, or in major or minor, the dominant function relative to the 1/1 harmonic
3rd mode in respect to 2nd mode is a fifth
@@ekstrapolatoraproksymujacy412 It's also exactly 1/3rd of a string relative to 1/1 of a string, 7th fret on the guitar is a fifth relative to 0th fret, it's the same relative to the 2nd mode tho, because the 2nd mode is just the octave!
It decides when it’s being measured because it is part of a conscious fabric.
It very well could be neutrinos and the positive and negative occurrences from it that hold the key
Is it still a problem of the measurement "device" interfering with what it's measuring?
What I came to as well.
I'm not an expert on any of this but I am still convinced the universe is a bunch of little electro-magnetic bubbles wobbling around one another with a different level of surface tension that allows a viscosity causing solid and semi-solid objects. The more these bubbles nestle themselves into one another's "cracks" or fields the higher the density and the stronger the object.